Several methods of forming sheet metal are known. A common method of forming sheet metal is stamping through the use of a die. However, casting a die is an expensive process. While a popular method of metal forming, the use of a die has certain disadvantages.
A variant of the use of a die in the formation of a metal workpiece is through a deep drawing process. In this process, a sheet metal blank is radially drawn into a forming die through the use of a punch.
Another known method of forming a workpiece is by way of incremental sheet forming. This is a technique where a metal sheet is formed step-wise into a finished workpiece by way of a series of relatively small incremental deformations. Sheet formation is accomplished using a round tipped tool that is typically fitted to a robotic arm. The tool forms the workpiece incrementally by repeated movements until the workpiece is fully formed.
One of the three key performance characteristics that determines the quality of incrementally formed workpieces is “dimensional accuracy.” The two main factors that influence dimensional accuracy are spring back of the (sheet metal) workpiece and stiffness of the various elements of the forming machine system. However, known forming tools do not always achieve the desired level of dimensional accuracy because such tools have large shanks that may interfere with formation of the metal workpiece through unintended contact with the vertical walls of the workpiece during the forming process.
Another hindrance to achieving the desired level of dimensional accuracy is that that that known tools have shanks that are tapered to meet the round tip and, as a consequence, the tip-to-shank interface is the weakest point on the load path of the entire forming machine. Known systems are thus prone to breakage at this point caused by stiffness of the forming tool and the inherent weakness of the tip-to-shank interface, a weakness that becomes particularly pronounced when deflection is experienced during the forming process.
Accordingly, finding an efficient and economical solution to mold vehicle interior components using a metallic pigment in the resin that avoids flow marks or dark spots while minimizing wastage is a desirable goal for automotive manufacturers.